Bacteria fossils or mere rock?

A team of British scientists analysed what has generally been accepted as the world's oldest fossils of bacteria, embedded in 3.5-billion-year-old rocks from western Australia, and they concluded that the rocks had never been more than non-living rocks. "None of the structures we see there we would interpret as fossils," said Martin D Brasier, a geobiologist at UK-based Oxford University and the lead author of the study. Rather, he said, the structures are merely tiny flaws in the rock, mineral filaments that formed around small crystals of silica. However, scientists led by J William Schopf, a professor of paleobiology at the University of California, USA, who first described the features as fossils in 1993, argue that they now have even better evidence that the features are indeed fossils.